From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f69.google.com (mail-it0-f69.google.com [209.85.214.69]) by kanga.kvack.org (Postfix) with ESMTP id 890E66B0038 for ; Fri, 15 Dec 2017 06:39:03 -0500 (EST) Received: by mail-it0-f69.google.com with SMTP id r6so14266170itr.1 for ; Fri, 15 Dec 2017 03:39:03 -0800 (PST) Received: from merlin.infradead.org (merlin.infradead.org. [2001:8b0:10b:1231::1]) by mx.google.com with ESMTPS id t6si2768081ioa.204.2017.12.15.03.39.01 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Dec 2017 03:39:02 -0800 (PST) Date: Fri, 15 Dec 2017 12:38:38 +0100 From: Peter Zijlstra Subject: Re: [PATCH v2 01/17] mm/gup: Fixup p*_access_permitted() Message-ID: <20171215113838.nqxcjyyhfy4g7ipk@hirez.programming.kicks-ass.net> References: <20171214112726.742649793@infradead.org> <20171214113851.146259969@infradead.org> <20171214124117.wfzcjdczyta2sery@hirez.programming.kicks-ass.net> <20171214143730.s6w7sd6c7b5t6fqp@hirez.programming.kicks-ass.net> <20171214205450.GI3326@worktop> <8eedb9a3-0ba2-52df-58f6-3ed869d18ca3@intel.com> <20171215080041.zftzuxdonxrtmssq@hirez.programming.kicks-ass.net> <20171215102529.vtsjhb7h7jiufkr3@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171215102529.vtsjhb7h7jiufkr3@hirez.programming.kicks-ass.net> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, x86@kernel.org, Linus Torvalds , Andy Lutomirsky , Borislav Petkov , Greg KH , keescook@google.com, hughd@google.com, Brian Gerst , Josh Poimboeuf , Denys Vlasenko , Boris Ostrovsky , Juergen Gross , David Laight , Eduardo Valentin , aliguori@amazon.com, Will Deacon , linux-mm@kvack.org, kirill.shutemov@linux.intel.com, dan.j.williams@intel.com On Fri, Dec 15, 2017 at 11:25:29AM +0100, Peter Zijlstra wrote: > The memory one is also clearly wrong, not having access does not a write > fault make. If we have pte_write() set we should not do_wp_page() just > because we don't have access. This falls under the "doing anything other > than hard failure for !access is crazy" header. So per the very same reasoning I think the below is warranted too; also rename that @dirty variable, because its also wrong. diff --git a/mm/memory.c b/mm/memory.c index 5eb3d2524bdc..0d43b347eb0a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3987,7 +3987,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, .pgoff = linear_page_index(vma, address), .gfp_mask = __get_fault_gfp_mask(vma), }; - unsigned int dirty = flags & FAULT_FLAG_WRITE; + unsigned int write = flags & FAULT_FLAG_WRITE; struct mm_struct *mm = vma->vm_mm; pgd_t *pgd; p4d_t *p4d; @@ -4013,7 +4013,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, /* NUMA case for anonymous PUDs would go here */ - if (dirty && !pud_access_permitted(orig_pud, WRITE)) { + if (write && !pud_write(orig_pud)) { ret = wp_huge_pud(&vmf, orig_pud); if (!(ret & VM_FAULT_FALLBACK)) return ret; @@ -4046,7 +4046,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, if (pmd_protnone(orig_pmd) && vma_is_accessible(vma)) return do_huge_pmd_numa_page(&vmf, orig_pmd); - if (dirty && !pmd_access_permitted(orig_pmd, WRITE)) { + if (write && !pmd_write(orig_pmd)) { ret = wp_huge_pmd(&vmf, orig_pmd); if (!(ret & VM_FAULT_FALLBACK)) return ret; I still cannot make sense of what the intention behind these changes were, the Changelog that went with them is utter crap, it doesn't explain anything. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org